Learning more about this game; i am asking what are the best position for O.K.H units, i mean,,where must there be,,in front of the battle,, back in Germany or is like the other HQs..

Also i see they have attached in turn 2 several units stacking in deep Germany, and i wanted thouse units to fight, so i have to move the O.K.H unit in front of the battle or is better to attach thouse units from O.K.H in others HQs,,¿what is the best?

Well the more commanders above a unit (without overburding the commandcap),the more chance an attack or hold will perform succesfully ,directly attached to the OKH =less rolls ,so it all depends up to you,most of the time i put the OKH in reserve and switch out bad units from the frontline for it ,i use them to fight but only in defense or reserve status or partisan duty,only last resort i will commit em ,thats how i always saw it

Gererally avoid having combat units directly attached to OKH involved in heavy fighting. Some rear guard actions, cleaning up pockets, holding the flank are a good way to use these units.

You should have enough Corps to attach your units too, although you may end up exceeding your Command capabilities while doing so. Try to avoid overloading your corps, if you have too, overload armies instead. Army Groups will (with the exception of AGN) be overloaded and it will take time to resolve.